In a bowl, combine 2 tablespoons cornstarch, 2 tablespoons
water and garlic powder until smooth.
Add beef and toss.
In a large
skillet or wok over medium high heat, stir-fry beef in 1 tablespoon oil until
beef reaches desired doneness; remove and keep warm.
Stir-fry broccoli,
carrots, celery and onion in remaining oil for 4-5 minutes.
Return beef to
pan.
Combine soy sauce, brown sugar, ginger and remaining cornstarch and
water until smooth; add to the pan.
Cook and stir for 2 minutes.
Serve
over rice.